1921] NATURAL SCIENCES OF PHILADELPHIA. 405 



hinge is heavy, set with thin, very close, vertical teeth, the tooth-row 

 being curved down a little at the posterior end. Basal margin very 

 coarsely fluted within. 



Length 11 7, alt. 106, diam. of right valve 56 mm. 



Area chiriquiensis Gabb. Plate XL, figs 2, 3, (Chiriqui), 4-6 (S. Domingo). 



Area chiriquiensis Gabb, Proc. A. N. S. Phila., 1860, p. 567, (1861). 



Area (Seapharca) chiriquiensis Gabb, Dall, Trans. Wagn. Inst., iii, p. 642. 



? Area patricia Sowerby, Q. J. Geol. Soc, vi, 1849, p. 52. 



The figures represent a type (Plate XL, fig. 2) and paratype (Plate 

 XL, figs. 3) . Plate XLI, figs. 1-3 are other specimens from the black- 

 ish shale at Chiriqui. It is equivalve, and the valves are alike ex- 

 cept that two or three more of the ribs are granulose in the left valve 

 than in the right. The prominent beaks are moderately to widely 

 separated by a broad, flat cardinal area marked with some angulate 

 grooves. The valves convex before the middle, flattened or even 

 very little concave behind it; about 10 posterior ribs in the left valve, 

 12 in the right, are nearly smooth, the rest being closely, or some- 

 times somewhat sparsely, granose. The ribs are weak on the pos- 

 terior slope. Intervening grooves are irregularly marked with 

 growth striae. 



Length 43, alt. 43 mm.; 29 ribs. 



Length 40, alt. 34, diam. 36 mm. ; 30 ribs. 



Length 73, alt. 70 mm.; 31 ribs (largest). 



Gabb subsequently considered A. chiriquiensis a synonym of 

 A. grandis, but it is not even closely related. 



The granulation is best developed in young or half-grown ex- 

 amples becoming more or less obsolete in old ones. The degree of 

 separation of the beaks also varies. The lot of about 40 examples 

 from Chiriqui, collected by Dr. John Evans, shows but little other 

 variation. 



Santo Domingan specimens (Plate XL, figs 4, 5, 6) are less ex- 

 tensively granose and the beaks are less widely apart than in many 

 of the type lot, though agreeing with others. The concavity be- 

 hind the middle is shghtly more marked. All of the specimens are 

 somewhat worn. 



Length 55, alt. 51, diam. of right valve 23 mm. 



Length 35, alt. 33, diam. 36 mm. 



Besides the above (no. 2722 Gabb Coll., numerous specimens), 

 some fragments were obtained by Mr. W. W. Webster on a stream 

 between Las Caobas and Hinche, Haiti. 



It appears likely that this species is the lost Area patricia of 



